1. Field of the Invention
The present invention relates to an apparatus for automatically changing an information storage medium which automatically effects loading or ejecting of an information storage medium into or out of an information processing device and automatically changes specified medium.
2. Description of the Related Art
An automatic disk changing apparatus, as fully disclosed in U.S. Pat. No. 4,742,504 (Takasuka et al.) employs a pair of cassette storage racks for storing a plurality of optical disk cassettes in an upright (vertical) position. A disk cassette manually inserted into the disk changing apparatus is loaded in a transfer device. The transfer device includes a rotatable carrier frame for holding the disk cassette and transferring it either to one of the storage racks or to an optical disk drive unit. To insert the disk cassette into the optical disk drive unit, the carrier frame is rotated through 90 degrees so that the disk cassette is loaded into the optical disk drive unit in approximately a horizontal position. When it is necessary to reverse the side of the disk cassette loaded in the optical disk drive unit with its side A operated, the disk cassette is taken out from the disk drive unit and held in the carrier frame of the transfer device. Then the carrier frame is rotated 180 degrees so that the disk cassette is reversed from side A to side B. After that, the disk cassette is loaded into the disk drive unit from the carrier frame so that side B of the disk cassette will be operated in the disk drive unit.
The carrier frame of the transfer device is operatively connected to a stepping motor via a pulley and a belt, and is tilted or inverted by rotation through 90 or 180 degrees by the action of the stepping motor.
However, in the automatic disk changing apparatus having the above structure, there may be occasions when the carrier frame of the transfer device fails to come accurately to a precise horizontal disposition with respect to the insertion port of the storage rack or the optical disk drive unit because of variations in the stopping position of the rotating shaft of the stepping motor or loosening of the belt. Then, since the stopping position of the carrier frame is maintained by the stepping motor, the stopping position of the carrier frame may be dislocated from the correct position by vibration or other external force.